Hydraulic draft gears



July 1, 1958 T. o. HENRlKsoN ETAL 2,841,294

HYDRAULIC DRAFT GEARS 5 Sheets-Sheet l Fiied June 4, 1956 7770?' O. H r'f'KSO/l Y Rafa/1d A. Mason IN V EN TURS 6H Mag fw MMM f f N um Y /QN 9 ANN vm mmmf, E

July 1, 1958 T. o. HENRIKSON ET AL 2,841,294

HYDRAULIC DRAFT GEARS 3 Sheets-Sheet 2 Filed June 4, 1956 R/ si? INVENTORS Thor' O. Henr/'kson BY Ro/cmd A. Magnuson vif WW MW July 1, 1958 T. o. HENRlKsoN ETAL 2,841,294

HYDRAULIC DRAFT GEARS 5 Sheets-Sheet 5 Filed June 4, 1956 .dlgi Patented July l, 1'358 aesinet rayonnante naher oisans Thor i). Henriksen md loiand A. Magnuson, Seattle, Wash., assigners to iaeiidc Sar and Foundry Company, Renton, Wash.

Application Enne 4, 1.956, Seriai No. 589,@40

Claims. (Ci. 21S-43) This invention relates to a hydraulic draft gear primarily for use in connection with railroad car couplings or the like and suitable for interchange with standard friction or rubber type devices of the same type.

This invention is particularly directed to a shock-absorber of the type in which shock loads are absorbed in part by throttling of hydraulic fluid under pressure through orifices, and in part by compression of gas contained within an expansible chamber by hydraulic fluid under pressure.

It is a primary object of this invention to provide an improved draft gear of economical construction whose operational characteristics approach a theoretrical ideal more closely than shock absorbers previously known. ideal characteristics include maximum shock absorption combined with a minimum peak force exerted upon the vehicle carriage frame or other structure which is to be protected. To attain this goal, it is necessary to absorb the applied shock load at a uniform rate, that is, to achieve a uniform application of force upon the vehicle carriage frame. This has previously been accomplished `by throttling hydraulic fluid through orifices whose crosssectional area is decreased as the displacement of the piston increases under application of a shock load, in such manner as to maintain a constant force upon the vehicleattached members. However, previous applications of this principle have required the use of valve means, other than the piston and cylinder, in combination with the throttling orifices, thus increasing the complexity and cost of the draft gear.

It is one object of this invention to provide an energy absorption device comprisingy a piston and cylinder, which combine to force uid contained in the cylinder through throttling orifices upon application of a load, and which further combine to decrease the cross-sectional areas of the throttling orifices in relation to their relative positions, and specifically in inverse relation to lthe piston displacement, Without employing additional valve means.

It is a further object of this invention to provide pneumatic means for further absorption of shock loads transmitted by pressurized hydraulic iiuid, for providing an expansible reservoir accommodating iluid transmitted through the throttling orices, and for storing of potential energy to aid in rapidly returning the piston and cylinder to their extended relative positions under unloaded conditions.

Another object is the use of an expansible exible gas-lled accumulator ybag within a chamber in the piston receiving uid from the throttling orifices, this accumulator bag being compressed by the entering iiuid by an amount equalV to the volume of piston displacement. When relative movement between the piston and cylinder ceases, the gas and iiuid pressures are equal, after which the expansion of the accumulator bag forces rapid return of the fluid through the throttling orices when the load is removed from the draft gear.

It is a further object of this invention to provide an improved Huid seal for a draft gear, comprising a exible impervious membrane sealed to both the cylinder and the piston, so that leakage of fluid from the draft gear is positively prevented.V In this connection, it is an additional object to provide means for maintaining a correct amount of iiuid within an enclosure of the seal although the volume of the enclosure varies with the relative positions of the piston and cylinder.

in connection with the previously stated object of providing xreans to aid rapid return of the piston and cylinder to their extended relative positions upon removal of a load from the draft gear, it is a still further object of the invention to provide means producing a force opposing the force exerted by the fluid within the seal enclosure in a direction tending to resist the piston return, so that the resultant force tends to aid a, rapid return. These means comprise an annular member associated with the piston and having opposite radial faces exposed to the seal enclosure and to a lluid-conlining space of larger cross-sectional area provided inthe cylinder, so that a larger force is exerted by the fluid in the cylinder space, tending to aid a rapid piston return.

Referring to the drawings:

Fig. 1 is a longitudinal section taken along line 1--1 of Fig. 4 of a recommended embodiment of the present invention, with parts shown in normal or no-load position;

Fig. 2 is a longitudinal section of the same device, with parts shown in their relative positions when the device is subjected to a load;

Fig. 3 is an axial section taken along line 3-3 of Fig. 2;

Fig. 4 is an axial section taken along line 4-4 of Fig. 1; and

Fig. 5 is a partial section taken on line 5 5 of Fig. 4.

In Fig. l, piston l@ is placed in axially-slidable relationship within the bore 12 of cylinder 1l, and is affixed at one end to a conventional follower 13 associated with suitable means for applying compressional loads to the draft' gear, or may be axed to a vehicle undercarriage frame. Similarly, cylinder l1 may alternatively be rigidly secured to a vehicle undercarriage frame, or may be aixed to means for applying compressional loads, such as a coupler or yoke. Such load-applying means form no part of this invention and are not shown, but may be selected as adapted to Various applications of the draft gear.

Cylinder 11 is also provided with a bore 14 of somewhat larger diameter than the piston l0. An annular ybushing l5 is slidably received by bore 14 and is maintained in rigid assembly with piston l@ by means hereinafter described. Thus, bushing l5 and that portion of piston 10 which contacts bore 12 comprise the bearing surfaces which maintain the concentric relationship of piston l0 and cylinder 11 While permitting relative axial movement of these members.

An annular seal i6 is provided to prevent escape of hydraulic uid from the draft gear, and for further objects to be described more fully hereinafter, and is formed at its inner and outer peripheries with lips 17 and 18. Seal 16 may preferably be made of nylon impregnated with a suitable ilexible oil-resisting compound, or of any suitable material combining qualities of strength, flexibility, and imperviousness to hydraulic fluids. -Lip 17 is seated in an annular groove 2? formed in the interior wall of cylinder 1l, and lip i3 is seated upon yan annular shoulder 2l formed on piston 1Q. Lip 17 is seated `firmly in groove 2li by means of annular sleeve 22, which is secured by externally threaded nut 23 engaging internal threads 24 formed in cylinder il. Lip i8 is seated firmly against shoulder 2l by means of castellated lock nut 25, castellated lock washer 26, and

{ Y bushing; k'. Circumferentially vspaced `grooves 27VVV are Y formed in the piston luto accommodate castellated lock washer 26.Y Piston 10 is providedwith circumferential VYcuring* locknut V2K5..

ally Within cylinder 11, abutting nut 23.

threads (not shown) formed `in the landsk circumferentiallysspacejd between grooves A27,Y for the purpose of se- Y As Aisevident' from the` above description, bushingl is securedv in rigid assembly`withpistonfltl by means Y -of loclcnut 25, loch washer 26, lip 18,'and shoulder.

AVlock'plate 3), as .best seen in Fig, 3, is placed axivln order to preventjpossible rotary movement of piston :16 in cylinder Y11, lwith consequent damage toseal 16,-the longitudinal yflats 32 'are formed Vin pistonY 19 to cooperate with' chordateportion 33-of 'lockplate-.St .inY XiallyY sliding relationship;V and loclcV plate 30 Vis ,further provided with cars 36 cooperating in died Vrelationship with longiI tudinal groovesS formedV in theY Walls of cylinder 11;. Referring again to Fig. l, chordateY-portion 33 "of lock plated@ further acts as a stop to prevent axail separa- Y tion 'of piston l@ and cylinder 11 beyond the desired stroke While handling and during assembly,r abutting shoulda-'34 of Apiston 10V tolimitV suchseparation. After mounting of .the assembled! draft gear en a vehicle car- ;-ternal chamber 40, passage La pair of conieally 'dis- Vposed,circumferentially' spaced passagewaysV 42, a-pair of longitudinally disposed groove-.5423, andV aY pair-,of longitudinal, circumferentially-spaced tapered groove passageways 43 shown in Fig. 5, which are spaced circumy terentially between grooves 42a.Y Passageways 42, 42a and 43 are shown in crossfsection'inrFigi 4. -lzfistonY is further provided with annular groove 44 and a series of radially disposed circumferentially spaced passages` 4&5. Passages'45 register with'a series of radially disposed cir Vcun'lferentially Aspaced passages 46formed1in-bushing 15, which is furtherV provided Withan annular` grooveY 47 about its periphery. Passages andgrooves 44, fi-5, 46,

47'establish a flow path connecting chamber-5l with enclosure 43 contained within seal le.

An expansible gas accumulator bag 5t?, formed of a ilaxible impervious material, is placed within chamber 4? through passage 41 prior to assembly/of the draft gear. TheV remaining space within chamberdconstitutes ahydraulic iluid reservoir. A fitting Si, having an internal gas valve, is inserted through stepped passage 53 formed in piston'l, and is assembled in threaded relationship with'ring'SS and lock-nuts S2 to secure the accumulator in place. The accumulator is charged with gas to a suitable pressurel through fitting 5 1, after which annular seal 57 is-'inserted in passage 53 and vthreaded cap 56 is placed in assembled relation with threadsd formed in passage 53. The gas accumulator bag'@ Yand gas fitting 51, 52, are of a type well known in the art, and form no part of the present invention. y

After insertion of accumulator bag Sti in chamber 49, a threaded cap 62 may'beinserted in passage 4:1 and secured by meansy of internal thread 6.5 formed in passage d1. A flanged Ymember 6h is slidably mounted withinan axial bore of -cap 62, and is retained by means of snapring 63 against the axial bias of compression spring 6l. Flanged member 6i) protects accumulator 5? against possible damage due to contactgwith the Walls of cham* ber'tl, in the eventuality that the accumulator should expand abnormally Vdue to uncontrollable accidental fac- Vtors. A threaded capA 64 Vis secured to cap 62 Vwithin threaded bore 63, forminr a smooth plane face for priston ld anda stop for seat 60. Chambers and passages the volume of'rchambe'r 66.1Fluid is forced through ta-V -pered passageways 43 ,and intotspace .67, Vthrough'pas--- sageways 42a, 42 and 41 into space dit, through passagesVr 4l-47 andinto space 4S contained within seal'16.` Pas-vY Y sageways 43 Vmay be dimensioned suitablyrtoabsorb a V56, 67,and 40.?48 are: lled with hydraulic Jluid,au ;l air is removed therefrom, by'suitable means Well known in the art l(not shown) Application of a load tortheifollower 13 in a .direct-'5 tion tendingto force pistoni@ further into fcylinderll, Y

toward the positionv ofV Fig.V 2, results in a reduction of substantial specified portion of the energy applied to the l' draft gear kby follower'l3, inu accordance with designed load capacity of the draft gear; Vand are tapered in such'.V Y, manner that a constant force will persist between cylinder Eiland piston rthroughout the stroke.- Asi-piston 10VV travels `further into 'bore 12, shoulder 69 formed by the intersection Vof bore l2 and 'bore' 1d .enclosesj smaller sections. of passageway a3, Yeljectively reducing the orifice area. The taperis'suchas to maintainra constant pressure in chamber 66 throughout the stroke of the piston and Vthusmaintain a constan applicationof force.'

v Fluid forced'into vchamber .40 willxco-mpress accumulator bag Sland the gas contained therein, thus storing potential energy in the accumulator bag to aid in` performing a `return stroke', to the positiontof Figsl, Vafter removal of the applied load from follovverile.Y Compression of theaccumulatorbag and the contained gas also serves to absorb the lremainder of the energy appliedto the draft gearvby follower 13,*ove1 and above the amount absorbedfas a concomitant'torfluid transfer under pressure through passageways d3.

By comparison of Figsl and 2,*itwill be'obvious that thek volume fof enclosureid within-seal lsincreasesappreciably during the energy-absorption stroke ofthe piston.

during the stroke, lluid, enters enclosure 4S'througl1 these passages anddgroovesgto :preventI such Yan occurrence.VV

During the return stroke, of;c Gurse,- the excess iluidiin enclosure't escapes'to chamberl bya 'returnowg ,The arrangement of seal16, bushngrlygroove 47,

and space 67 also serves to provide an additional force tendingtoreturn the r,piston `to the no-load positionof Figi, upon release of the loa'dfrom follower '13. ',Referringrto Fig. 2, arrow A lrepresents the `hydraulicliorce exerted upon bushing 15,V partially through nut 25 and lock-washerl,'tending ,to aidgthe return stroke. Similarly, larrow/v E -represents the hydraulic forceexelted upon. bushnal tending. to. resist the return stroke. .The uid pressuresexisting in enclosure 48 and space 67'will be substantially equal, sotthatgtheunbalanced force' acting'upon bushing 15 -will be proportional to the difference in `effective crossfsectional areas ofrbushing 15 axially Investigation has revealed lthat the effective load position'of Fig. l.

As an effectief the work expended while ,the fluid isV forced through passages 3, the temperature of'theguid `will rise considerably. lt would notV be practical nor desirable to enposejthe accumulator bag and sealV 16 to this high Vtempt-:rature oil. This device thereforek allows the active fluid to mix with the relativelyy cool joilV in chamber 67Y andto come in contact` with the relatively coolwalls of cylinderr'll, before it `is directed'through passages 42, where lfurther cooling occurs before the fluid reaches reservoirtt). VK'It should also beV noted that fdi'sc 69 also servesY the purpose of diverting the oil stream,

To prevent collapse of seald iupronitself,` passagesr and grooves 414-47 areprovided; vasV previously discussed;r

as it enters the reservoir, thus preventing high velocity oil from striking the accumulator bag directly.

Another important feature in this device is that the high pressure chamber 66 is isolated from seal 16, which is thus protected from high pressure loads developed during impact. It should also be noted that seal 16 rolls on and off the surfaces to be sealed with no rubbing action and consequent high ratio of wear, which are associated with seals commonly used in connection with hydraulic devices.

What we claim is:

1. In a hydraulic draft gear comprising a piston and cylinder assembled for relative axial movement and defining a hydraulic huid-confining chamber, an expansible hydraulic iiuid reservoir formed in said piston, and throttling passageways interconnecting said chamber and said reservoir; the combination of an annular impervious exible fluid seal atiixed to said piston and to said cylinder and forming a huid-filled enclosure in cooperation therewith, and passages interconnecting said enclosure with said reservoir, such that variation in the volume of said enclosure, consequent upon said relative axial movement of said piston and said cylinder, will be accompanied by a compensating iiuid transfer between said fluid enclosure and said reservoir through said passages.

2. ln a hydraulic draft c'ear comprising a piston and cylinder assembled for relative axial movement, a hydraulic uid-conning chamber formed in said cylinder, an expansible hydraulic fluid reservoir disposed in said piston, and throttling passageways interconnecting said chamber and said reservoir, such that said relative axial movement is constrained by hydraulic fluid transfer between said chamber and said reservoir through said throttling passageways; the combination of an annular impervious exible iiuid seal aihxed at its inner periphery to said piston and at its outer periphery to said cylinder, and forming a uid-lled enclosure in cooperation with portions of said piston and said cylinder; and passages interconnecting said fluid enclosure with said reservoir, such that variation in the volume of said uid enclosure, consequent upon said relative axial movement of said piston and said cylinder, will be accompanied by a compensating iiuid transfer between said fluid enclosure and said reservoir through said passages.

3. In a hydraulic draft gear comprising a piston and cylinder assembled for relative axial movement, a hydraulic iiuid-conning chamber and an expansible hydraulic iiuid reservoir, throttling passageways interconnecting said chamber and said reservoir, a flexible seal for the apparatus partially confining a fluid enclosure, and tiuid passages connecting said enclosure with said reservoir; means for aiding rapid return of the piston from a rst position assumed under an applied force to a second position upon removal of said applied force; said means comprising, in combination, an axial bore formed in said cylinder and enclosing an annular Huit -confining space surrounding said piston over a portion of its length, said throttling passageways connecting said chamber and said space, and an annular member aixed to said piston and having opposite radial faces axially conning said space and said enclosure, respectively; said radial face coniining said space being or larger area than said radial face confining said enclosure, such that the resultant force exerted by uid of approximately equal pressure upon said opposite radial faces Will be in a direction aiding the return of said piston to said second position.

4. In a hydraulic draft gear, a cylinder formed with a rst hydraulic uid-conning axial bore and with a second superimposed hydraulic fluid-confining axial bore of larger diameter and shorter length, a piston cooperating along an end portion of its peripheral surface in axially slidable bearing engagement with said iirst bore, longitudinal circumferentially spaced grooves formed in said peripheral surface of said piston, a rst group of said grooves being of tapered form and communicating with said tirst and second bores, a second group of said grooves communicating with said second bore, an expansible hydraulic fluid reservoir formed in said piston, and passageways connecting said reservoir with said second group of said grooves; whereby the areas of communication of said grooves with said second bore are varied by relative axial movement of said piston and said cylinder.

5. In a hydraulic draft gear, a cylinder formed with a first hydraulic fluid-confining axial bore and with a second superimposed hydraulic Huid-confining axial bore of larger diameter and shorter length, a piston cooperating along an end portion of its peripheral surface inaxially slidable bearing engagement with said first bore, longitudinal circumferentially spaced grooves formed in said peripheral surface of said piston, a first group of said grooves being of tapered form and communicating with said first and second bores, a second group of said grooves communicating with said second bore, an expansible hydraulic fluid reservoir formed in said piston, and passageways connecting said reservoir with said second group of said grooves; whereby the minimum crosssectional areas of communication between said first group of said grooves and said second bore deiined by the cooperation of said first bore with said iirst group of said grooves, and the areas of communication of said second group of said grooves with said second bore, are varied by relative axial movement of said piston and said cylinder.

6. The combination of claim 5, together with an annular member aixed circumferentially to said piston and slidably engaging said second bore in duid-tight relationship; an annular impervious flexible fluid seal aixed at its inner periphery to said piston and at its outer periphery to said cylinder, and forming a Huid-confining enclosure in cooperation with said piston, said cylinder, and said annular member; and passages interconnecting said fluid enclosure with said reservoir; such that variation in the volume of said enclosure, consequent upon relative axial movement of said piston and said cylinder, will be accompanied by a compensating fluid transfer between said enclosure and said reservoir through said passages.

References Cited in the iile of this patent UNITED STATES PATENTS 713,691 Schneider et al Nov. 18, 1902 1,936,788 Hardy Nov. 28, 1933 1,955,349 Stevens Apr. 17, 1934 2,187,625 Mercier Jan. 16, 1940 FOREIGN PATENTS 1,113,867 France Oct. 22, 1954 528,569 Germany June 24, 1928 740,112 Great Britain Nov. 9, 1955 

